package day03;

public class Demo03 {
    public static void main(String[] args) {
        String s = "A";
        StringBuilder ss = new StringBuilder("A");
        append(s);
        append(ss);
        System.out.println(s);
        System.out.println(ss);
    }
    public static void append(String s){
        s+="A";
    }
    public static void append(StringBuilder s){
        //s.append("A");
        s = new StringBuilder("AA");
    }
}
